Photographic emulsions containing molecular compounds of mercuric salts with amines



1, 2,728,663 Patented Dec. 27, 1955 PHOTOGRAPHIC EMULSIONS CONTAINING M- LECULAR COMPOUNDS 0F MERCURIC SALTS WITH AMINES Charles F. H. Allemlohn R. Byers, Jr., and Thomas F.

Murray, Rochester, N. Y., assignors to Eastman Kodak fompany, Rochester, N. Y., a corporation of New ersey No Drawing. Application November 8, 1952, Serial No. 319,611

20 Claims. (Cl. 95-7) This invention relates to fog-inhibiting agents and stabilizers for photographic emulsions and to photographic camera. General fog is formed in a number of ways. It

may be caused by the conditions of high temperature or humidity or unusually long time of storage. The nature of the emulsion may also produce chemical fog as well as the conditions of development of the-emulsion as by development for protracted periods of time or at temperatures above normal. fog and sensitivity changes in photographic filmsproduced by storage under adverse conditions of temperature and humidity or for prolonged periods of time before exposure and development.

General fog and loss of sensitivity of the emulsion are especially likely to occur when the sensitive material is stored under conditions other than ideal, that is, under conditions of high temperature. and humidity, as in tropical regions.

It is an object of the invention to provide novel antifogging or fog-inhibiting compounds for emulsions. A further object is to provide anti-fogging agents which stabilize the initial sensitivity of the emulsion. A still further object is to provide anti-fogging agents which improve the keeping of the emulsion in tropical regions. Other objects will appear from the following description of our invention.

These objects'are accomplished by incorporating in a silver halide emulsion a molecular compound of a mercuric salt with an amine'or with a salt of an amine.

The principal purpose of our invention is to provide a means for maintaining the sensitivity and fog of silver halide emulsions at or close to initial optimum values under keeping conditions of high temperature and humidity. The fog inhibitors which we propose to use are added to the emulsion at any stage during the process of manufacture prior to coating the emulsion to avoid loss of sensitivity and to inhibit the growth of incubation or keeping fog with passage of time under non-ideal conditions of storage. The mercury fog inhibitor may be added to the emulsion in solution in any convenient solvent not injurious to the emulsion'such as water, lower alcohols and ketones. V v

A solution of the mercuric compound which we employ when added in suitable concentration before coating to unsensitized or optically sensitized silver halide emulsions usually does not appreciably afiect the sensitometric values for sensitivity and fog when measurements are made soon after coating.- Howevenwhen sensitometric meas-,

We. are primarily concerned with United States Patent'Oflice urements are made after appreciable intervals of time our invention:

under tropical or dry'conditions of storage at elevated temperatures, these compounds do stabilize photographic speed and maintain fog at a low level.

The following compounds may be used according to Molecular compounds of mercuric salts with amines or salts of amines "Q-amino-fiJodopyfldine mercuric iodide" Bis(fi-amino-fi-iodopyridine) mercuric iodide -rn -HgIs N// NH:

Bis(Q-amino-S-iodopyridine hydroiodide) mercuric iodide -Hg(COOCHr)r Bis(2 aminopyi r idine) mercuric acetate Bis(4amino-S-iodopyridine)hydroiodide mercuric iodide Bis(2-aminobenzothia zole hydrobromide) mercuric chloride 2-aminobenzothiazole hydrobromide mercuric iodide --.-Pyridlne hydroiodide' mercuric iodide Z-uminopyridlnmmercuric iodide I m-(Qninolinohydmidide)= mercuric iodides m- (Benzothia zele mzdnoindide) amercurieiiodide o-cmm Hale lso 2-am1no-5-iodo derivative I CQ/HE \I. w(2-aminoquinoline ethiodide) ,.mercuric iodide OH- -HgI2 on t a:

a;(Benzothiazo1e methiodide) mercuric iodide CH5 I Z w (Z-ioclopyridine.methiodide) mercuric iodide Bie(2 metl1y1benzothiazo1e hydroiodide.) mercuric iodidev Bis(s-amino-figodoquinqline hydroiodide) mercuric iodide 4-nitro-dimethylaniline mercuric iodide- The preparation: of silver halide. emulsions involves three separate-operations? 1) ,th'e emulsification and digestion orsripening of the silver halide, (2) thefreeing of theemulsion from aqueoussoluble' salts usually" bywashing; (3") athecsecondidigestion or after-ripening: to obtain increased? sensitivity (Mees; The-zTneory of the PhotographioProcess; 1942', page. 3) may be added at anystage; e.=. g.-, after :the :final digestion;

The mercury compounds are useful "generally in photographic; silver halide developing: out emulsions; They may; b'eused ,inremulsions vchemically-sensitized .with sulfur compounds,:.reducingagents omnoblennetals such as gold orrbws va'rious combinations:- of-: theseras: described a more fully hereinafter.

The most useful concentrationrofifogtinhibitor .is from about. 10:05:5t0 :1 .Oimg: :of ifogzinhibit'or :permole: of silver halidein;.the.-:emulsi nr.. Althoughhigher amountsmaybe usedawe havefound: that few emulsions are :likelyio toleuatez-as; muchas: 5: times thissupperlimit. without serious desensitization;

The :emulsionst: may be chemically;. sensitized by any of the accepted procedures; for example,:.they mayzbe= digestedzwitlrnaturally -active:gelatin; .o1::sulfureompoimds mayz be:addedcsuchzasithoseadescribed:inzSheppardzIL. Sp.

Patcntsgl;ii74,'944,.and 1;6.23,499,=and:Sheppard and-Brlg.-. ham'zruu 3;. Patent; 2,410,689r

The; emulsions;may also"be;.treated with, salts ofathe noble metals; such as ruthenium, rhodium, palladium; iridiumrandi-platinum,,all oflwhichzbelonguto .group VIII oflitheeperiodic ,table of elements: and :have; an: atomic weight'tgreeten than, .1 00. Representative :compounds' are ammonium chloropalladate,, potassium: chloroplatinate;

and sodium :chloropalladitq; .whichuare. :used. for: sensitizing;in, -amounts, zbBlOW that ;which -.-produces1 any. substantiakfog inhibition iasr described iniSmith:and-TrivelliU. S. Patent 2,448,060,- and iaswantifogggntsrin higher. .amounts, aszdescribedin. Trivelh,and Smith :U. S.'Patents 2,566,245 and 2,566,263.

Thewemulsionsrmay also .be..chemically-.,sensitized..witl1 gold jsaltsvas described; in Waller and DoddfU Sv Patent 2,399,083; D'amschroder UI. Sf Patent 2,597,856, and Yutzy-and lieermakers U5 SI Patent $597,915! Suitable compoundsare potassium. chloroanrite, potassium aurithio'cyanate; potassium chloroaurate; auric trichlo= r d and" 2 aurosulfobenzothizizole-methochloridee The-fog inhibiting agents The emulsions'may also'be chemieallysensitiz'ed'with reducing agents such as stannous salts (Carroll U. S. Patent 2,487,850), polyamines such as diethylene triamine (Lowe and Jones U. S. Patent 2,518,698), 'poly- V U I V bation as in Example I, the following results were obamines such as spermine (Lowe and Allen U. S. Patent 2,521,925), or bis-(fi-aminoethyl) sulfide and its watersoluble salts (Lowe and Jones U. S. Patent 2,521,926).

of silver halide per liter,-: and digested with a sulfursensi tizer such as disclosed in Sheppard U. S. Patent 1,574,944, and potassium chloroaurate. Upon development and testing for speed, gamma and fog, before and after incutained Compound Fresh Test After Incubation Speed Gamma Fog Speed Gamma Fog Conn-01... (2gmlno-5-iodopyridineh-2HL ZHI-Hgh (2 amino 5 lodoqulnoltneh 2HI-HgI 1. 0 860 l. 78 11 1, 100 1. 63 ll 1. 0 800 '1. s1 12 an 1. 92 .00 1.0 840 1. 94 .10 1,120 I 1. es 14 saponin solution, there were added the amounts of mercuric salts in methyl alcohol solution shown in the following table, the amount of mercuric salt being calculated per mole of silver halide. The emulsion was coated on glass plates, and the coated plates together with other plates coated at the same time and with the same emul sion to which no mercuric salt had been added, were exposed on an Eastman type Ib Sensitometer and developed for five minutes at 68 F. in a developer of the following formula:

- Grams N-methyl paraminophenol sulfate 2.5 Sodium sulfite (desiccated) 30 Hydroquinone 2.5 Sodium metaborate Potassium bromide 0.5

Water to 1 liter.

The plates with and without the mercuric compounds were held at 120 F. and relative humidity for one week and were then exposed and developed as indicated. The results of tests for speed, gamma and fog were as follows: r

EXAMPLE 3 A silver halide emulsion which had been chemically sensitized with a mixture of gold and sulfur sensitizers to which a reducing agent had been added, was tested with and without a mercury compound, in the following way:

One liter of a gelatino silver bromoiodide emulsion containing 0.24 mole of silver halide per liter was digested with a sulfur sensitizer such as disclosedin Sheppard U. S. Patent 1,574,944, and potassium chloroaurate, under conditions leading to the maximum speed in the final emulsion but without causing any appreciable fogging of the emulsion. A portion of the emulsion was then coated and dried.

After digestion to maximum speed there was added to the emulsion containing the sulfur and gold sensitizers a methanol solution of 0.01 g. of triethylene tetramine per mole of silver halide and the mixture digested for 20 minutes at 40 'C., after which the emulsion was coated on a suitable film support. To other portions of emulsion digested with triethylene tetramine there wasadded prior .to coating varying amounts of (Z-amino-S- iodopyridine)z-2HI-Hglz. The resulting films were exposed on a Ib Sensitometer which gives intensity scale exposures to light of sunlight quality, and developed for 4 minutes at 20 C. in a developer of the following composition:

. Grams N-methyl-p-aminophenol sulfate 2.2 Sodium sulfite (desiccated) 96 Hydroquinone 8.8 Sodium carbonate, monohydrate 56 Potassium bromide 5 Water to 1 liter Fresh Test Alter Incubation Compound rug/mole S eed Gamma Fog .Speed Gamma Fog 0011001 540 1.62 .08 500 1.55 .13 (2 amino 5 -iod0 pyrldlneh- 2HI-Hgh 1.0 470 1.08 .06 420 1.61 .03

EXAMPLEZ The coatings with and without the mercuric comvCoatings were mad e as in Example 1 using a gelatino-silver bromoiodide emulsion, optically sensitizedpounds were held for one week at F. and 20% relative humidity and were then exposed and developed in the same way as in Example 1, containing 0.24 mole 76 as indicated.

. The following sensltometric results were obtained: testing for speed, gamma and fog, before and after in- 1 a Fresh Test After Incubation Compound v mg./mole V V Speed Gamma Fog Speed Gamma Fog Control 12a 1. so .03 112 1. 21 .35 (I) Reduction sensitized with Triethylene tetramine 220 1. 45 04 98 1. 23 49 I+Hg compound 0. 2 185 1. 45 .05 138 1.18 .30 I-l-Hg compound 0. s 105 1. 45 .04 13s 1. 2e .14

EXAMPLE 4 cubation for 4 weeks at 120 F., the following results A positive-speed gelatino-silver. bromoiodide, emulsion was prepared and digested with a sulfur sensitizer and a gold salt as in Example 3.

This emulsion was divided ino three portions and one portion was digested for 30 minutes at 40 C. with 400 mg. of fi,fl-diamino diethyl sulfide dihydrochloride per mole of silver halide.

To a portion of the latter there was added 0.4 mg. of (2-amino-5-iodopyridine)2-2HI'HgIz per mole of silver halide, and all three portions were coated.

The resulting coatings were exposed on a Ib Sensitometer and developed for 5 minutes in a developer of the following composition:

were obtained:

I Fresh Test After Incubation v Compound Speed Gamma Fog Speed Gamma Fog o Control 255 1. 24 O9 210 1. O9 50 Mercury 111 pound 0195 265 1. O8 200 1. 22 28 EXAMPLE 6 A gelatino-silver bromoiodide emulsion was chemically sensitized with sulfur and gold sensitizers as in Example 3 and was then digested to optimum speed and N th 1 h 1 1ft e divided into portions to which were added the various 'gi 'g g mercury antifoggants shown in the following table. e eslcca e 6 These portions were coated and exposed on 'a Ib Sensiy .roqumone tometer and developed for five minutes in a developer Sodium Carbonate, monohydrate 22-5 of the following composition. Potassium bromide 0.9 Grams cltnc N-methyl-p-aminoph'enol sulfate 2.5 Potasslum metabisulfite -n 1.4 Hydmquinone 2 5 water to 1 met Sodium sulfate (desiccated) 30 Other coatings were incubated as in Example 1. Upon Sodium metaborate 10 testing for speed, gamma and fog the following results Potassium bromide 0.5

were obtained:

. Water to 1 liter Fresh Test Alter Incubation Compound mgJmole 3 Speed Gamma Fog Speed Gamma Fog Control ss 2. 27 .03 90 1.82 .00 (1) Reduction sensitized with B,B-dlamlnodiethyl sulfide dl-HCI 400 115 2. 30 04 100 1. 70 7'1. I+Hg compound 0. 4 98 2. 43 04 130 1. 71-

EXAMPLE 5 Upon testing for speed, gamma and fog, before and after A medium-speed gelatino-silver bromoiodide emulsion was digested with 20 mg. per mole of silver halide of allylincubation as in Example 1, the following results were obtained:

- Fresh Test After Incubation Compound mg./mole Speed Gamma Fog Speed Gamma Fog Control 1,500 .08 1,450 0.81 .19 Bis(2-aminobenzothiazoleHD- HgIz 0. 1,800 0.80 .03 1,780 0.76 .10 (2-aminobenzothinzole-HBr)- HgBr; 0.24 1,500 0.83 .07 1,750 0.70 .08 Pyridine HI-HgIg 0--. 0. 06 1, 500 0. 81 06 1,120 0. 82 .06 x(benzothiazoleme-thiodide)- HgI; 0.96 1,400 0.79 .06 1.320 0.75 .07 x(2-omlnobenzothiazole methlodide)HgI: 0.06 1,480 0.80 .07 1,380 0.70 .07

EXAMPLE 7 thiourea and divided into two portions to one of which there was added 4-nitro-dimethy1aniline hydroiodide mercuric iodide as shown in the following table. Each of these emulsions wasicfoated-on i-a 'cellulose. acetate support and-the coatings were exposed on a Ib'Sensitom-' eter anddeveloped for four minutes in a' developer of the same composition as that used in Example 3-;T" Upon varyingamounts of 4-nitrodimethylaniline hydroiodide mercuric iodide as shown in the following table. These emulsions were coated on' a' cellulose acetate support, exposed on a Ib Sensitometer and developed for 3 minutes in a developer having the same composition as that used in Example 3. Upon incubation and testing the samples as in Example 3, the ,following results were obtained:

Fresh Test After Incubation Compound 1 Speed Gamma F g Speed Gamma Fog Control 420 .79

Mercury compound .0275 290 99 09 430 68 18 Do 055 450 86 08 360 82 16 D 0825 370 87 09 490 66 16 The compounds listed above were prepared as follows:

Compound 1.2-amino-5-iodopyridine mercuric iodide Compound 2.Bis(Z-aminobenzothiazole hydroiodide) mercuric iodide To a solution of 22.7 g. (0.05 mole) of mercuric iodide and 25.6 g. of 50% hydroiodic acid in 100 cc. distilled water was added, with stirring, 15 g. (0.1 mole) of 2- aminobenzothiazole. The mixture was heated on the steam bath for 30 minutes. During this time an oil separated. This oil was dissolved by slowly adding absolute ethyl alcohol. The solution was treated with a small amount of Norit (decolorizing carbon) and filtered hot. Upon cooling, the new compound crystallized. The crystallization was finished by the addition of a small amount of water, and the product was filtered and dried. There was obtained 48.6 g. (48% of the theoretical amount of 100.8 g.) of the product which had a M. P. of 164- 166 C.

Compound 3.Bis(2-amino-5-iodopyridine) mercuric iodide Compound 4.--Bis(2-amino-5-i0dopyridine hydroiodide) mercuric iodide 90.8 grams of mercuric iodide were dissolved in a solution of 101 grams of 57% hydriodic acid, which had been freshly distilled from hypophosphorous acid, dissolved in 1100 cc. of distilled water. This solution was filtered into a 4-liter beaker and to it was added with stirring a filtered solution of 88 grams of mercury-free 2-amino-5- iodopyridine dissolved in 1100 cc. of absolute ethyl alcohol. This was cooled with stirring to'0 C. in an ice salt bath, and filtered. There were obtained 189 grams, M. P. 183-185 C., of tan-colored product. This is 67.7% of the theoretical amount of 279 grams.

Compound 5.Bis(2-aminopyridine) mercuric acetate Z-aminopyridine (1.84 g.) was dissolved in water (16 cc.),and mercuric acetate (2.56 g.) was added and the whole heated for 2 minutes The white powder was collected and washed thoroughly with ethanol after which it had M. P. 166167.'

1o Compound 6.-Bis(4-dmino-3-iodopyridine) hydroiodide mercuric iodide This compound was made by the same method as that used for Compound 4, using 4-amino-3-iodopyridine instead of 2-amino 5-iodopyridine.

Compound 7.-Bis(Z-aminobenzoihiazole hydrobromide) mercuric chloride Z-aminobenzthiazole hydrobromide (2.3 g.), mercuric chloride (1.35 g.) and ethanol (10 cc.) were boiled to dissolve and allowed to cool. Glassy aggregates (3.3 g.) separated. They formed colorless aggregates, M. P. 162- 164, from ethanol.

Compound 8.2-aminobenzothiazole hydrobromide mercuric bromide Z-arninobenzthiazole hydrobromide (2.3 g.), mercuric bromide (1.8 g.) and ethanol (10 cc.) were warmed gently for 2 minutes until dissolved. The addition of water precipitated an oil which soon crystallized. It (3.2 g.) formed fiat, colorless needles, M- P. 168-170, from ethanol.

Compound 9.2-aminobenzothiazole hydrobromide mercuric iodide 2-aminobenzthiazole hydrobromide (2.3 g.), mercuric iodide (2.27 g.) and ethanol (10 cc.) were heated for 2 minutes to dissolve then poured into water. The yellow oil crystallized rapidly. It (3.5 g.) formed yellow. needles,

M. P. 158, from glacial acetic acid.

Compound 10.-Pyridine hydroiodide mercuric iodide Pyridine (0.8 g.), hydriodic acid (s. g. 1.97) (2 cc.), mercuric iodide (4.5 g.) and ethanol were heated gently with swirling. The iodide dissolved rapidly. Gradual cooling caused the whole to solidify. It (5.8 g.) after washing with a little ethanol was obtained as pale yellow flakes, M. P. 174, from ethanol or acetic acid.

Compound 11.--2-aminopyridine mercuric iodide Mercuric iodide, 4.54 g., and 2-arninopyridine, 2 g., and chloroform, 15 cc. were heated under a refluxing condenser until the red color of the mercuric iodide had disappeared. The solution was filtered, concentrated to incipient crystallization and cooled. The pale yellow crystalline'product was filtered and dried. There was obtained 2.2 g. of Z-aminopyridine mercuric iodide, melting at 131 C.

Compound 12.-x( Quinoline hydroiodide) mercuric iodide Quinoline (1.3 cc.), ethanol (10 cc.), hydriodic acid (s. g. 1.97) (2 cc.) andmercuric iodide (4.5 g.) were warmed gently to dissolve. The'product oiled out on cooling, then it solidified. It (5.0 g.) after an ethanol wash formed yellow crystals, M. P. 162, from ethanol.

Compound 13.x(Benzothiazole hydroiodide) mercuric iodide Benzothiazole (1.3 cc.), ethanol (10 cc.), hydriodic acid s. g. 1.97' (2 cc.) and mercuric iodide (4.5 g.) were warmed gently together to dissolve. The product oiled out, thencrystallized on chilling. It (6.5 g.), formed colorless blades, M. P. 93-96, from ethanol.

Compound 14.'-Bis(Z-nzethylbenzothiazole hydroiodide) mercuric iodide Z-methylbenzthiazole (1.4 cc.),ethanol (10 cc.), hydriodic acid, s. g. 1.97 (2 cc.) and mercuric iodide (4.5 g.) were heated to dissolve. The product then crystallized from the hot solution. It, (5.7 g.-) formedv pale yellow needles, M. P. 178, (softens at ca. 158). from ethanol.

anemone '21?! Compound .15-.--Bis(8-amino-5-iodoquin0line hydroiodide) mercuric iodide This compouiid wasvmade by the same method as that used for Compound 4, using 8-amino-5-iodoquinoline instead of 2-amino-5-iodopyridine.

Compound 16.--x(2-aminoquinoline ethiodide) mercuric iodide Z-aminoquinoline ,ethiodide (3.0 g.) mercuric iodide (4.5 g.) and ethanol (100 cc.) were refluxed to dissolve. The crystals (7.2 g.) were collected after chilling and formed heavy yellow prisms, M. P. 186l88 from ethanol.

Compound 17.x(.Benzothiazole methiodide) mercuric iodide This compound wasprepared .by the method .used to prepare Compound 18, using the simple 3-methyl benz' thiazoline instead of the Z-imino derivative.

Compound 18.x(Z-aminobenzothiazole methiodide) mercuric iodide 2 imino 3 methylbenzthiazoline (1.65 g.), mercuric iodide (4.54 g.), hydriodic acid, s. g. 1.97 (2 cc.) and ethanol cc.) were heated for 2 minutes on a steam bath. The iodide dissolved as a crystalline precipitate formed. It (5.5 g.) was collected after chilling, washed with ethanol and obtained as pale yellow crystals, M. P.

202-205 from ethanol.

Compound 19.x(2-iodopyridine methiodide) mercuric iodide 2-iodopyridine methiodide (3.5 g.), mercuric iodide (4.5 g.) and ethanol (20 cc.) were refluxed for minutes. It (7.1 g.) formed a yellow powder, M. P. l78179, from much ethanol.

Compound 20.x(2-iodoquinoline methiodide) mercuric iodide 2-iodoquinoline methiodide (4.0 g.), mercuric iodide (4.5 g.) and ethanol cc.) were refluxed for 15 minutes. The heavy yellow precipitate (6.5 g.) formed yellow needles, M. P. 154-155 from much ethanol.

Compound 21 .a,u',Dipyridyl hydroiodide mercuric iodide This compound was made by the same method as that used for Compound 4, using a,a'-dipyridyl instead of 2- amino-S-iodopyridine.

Compound 22.4-nitro-dimethy[aniline mercuric iodide To a solution of 3.3 grams of 4-nitrodimethylaniline in 100 cc. of absolute ethyl alcohol there was added 4.5 grams'ot Hgla, andthe mixture heated under reflux until the'red .color disappeared. The solution was filtered hot, cooled and againfiltered. The solution was concentrated to one-fourth volume and cooled, whereupon'the product crystallized out as crystals having a melting point of ISO-155 C.

Compound 23.-Melamine mercuric chloride Compound 24.Hexamethylene tetramine allyliodiae mercuric chloride This compound was-prepared by the same method -.as Compound 25, using hexamethylene tetramine alloiodide instead of the simple hexamethylene tetramine.

Compound125. Hexdmethylene tetramine dimercuric chloride 'g. (0.2 mole) mercuric chloride in cc. of absolute ethyl alcohol. There was an immediate precipitation of a white solid. 'The mixture was permitted to stand at room temperature for three hours. After it was filtered, the mixture was washed once with 50 cc. absolute ethyl alcohol and dried. The yield of hexamethylene dimercuric chloride which decomposed at 235 C. was almost quantitative.

Compound 26.Cystein hydrochloride mercuric chloride This compound was prepared by the same method as Compound .23, using cystein hydrochloride instead of melamine.

Instead of incorporation in the silver halide emulsion the fog-inhibitors of .our invention may be incorporated in a colloid layer such as a gelatin layer on one or both sides'of the support or they may bc'incorporated in a processing bath such as a developer or pre-bath.

The fog-inhibiting agents which we have described may be used in various kinds of, photographic emulsions. In addition to being useful in ordinary non-sensitized emulsions they may also be used in orthochromatic, panchromatic and X-ray emulsions. If used with sensitizing dyes, they may be added to the emulsion before or after the dyes are added. Various silver salts may be used as the sensitive salt, such as silver bromide, silver iodide, silver chloride or mixed silver halides. The mercury compounds may be used in emulsions intended for color photography, for example, emulsions containing colorforming couplers, or emulsions to be developed by solutions containing couplers.

The dispersing agents may be gelatin or other colloid such as collodion, albumen, cellulose derivatives or synthetic resins.

It will be understood that we contemplate as included within our invention all modifications and equivalents falling within the scope'of the appended claims.

We claim:

1. A light-sensitive silver halide emulsion containing a small amount of a molecular addition compound of a mercury salt with a nitrogen compound of the class consisting of (1) heterocyclic nitrogen compounds in which at least 3 bonds of the heterocyclic nitrogen atom are attached to carbon, (2) amine-substituted mononuclear aromatic compounds in which 3 bonds of the aminonitrogen atom are attached to carbon, (3) their halogen acid salts, and (4) the halogen acid salts of aliphatic amines containing at least 3 carbon atoms.

.2. A light-sensitive silver halide emulsion containing a small amount of a molecular'addition compound of a mercury salt with a halogen acid salt of a heterocyclic nitrogen compound in which at least 3 bonds of the heterocyclic nitrogen atom are attached to carbon.

3. A light-sensitive silver halide emulsion containing a small amount of a molecular addition compound of a mercury salt with a halogen acid salt of a primary amine substituted heterocyclic nitrogen compound in which at least 3 bondsof the heterocyclic nitrogen atom are attached tocarbon.

4. A. light-sensitive silver halide emulsion containing a small amount of a double salt of a pyridine hydrohalide and a mercuric salt.

. 5. .A light-sensitive silver. halide emulsion containing a small amount of a double salt of a pyridine hydroiodide and amercuric. halide.

6. .Alight-sensitive silver halide emulsion containing a small amount of a-double salt of a 5-iodopyridine hydroiodide and a mercuric halide.

7. A light-sensitive silver halide emulsion containing a wvw vspasms 13 small amount of bis(Z-amino-S-iodopyridine hydroiodide) mercuric iodide.

8. A light-sensitive silver halide emulsion containing a small amount of his (4-amino-3-iodopyridine) hydroiodide mercuric iodide.

9. A light-sensitive silver halide emulsion containing a small amount of pyridine hydroiodide mercuric iodide.

10. A light-sensitive silver halide emulsion containing a small amount of bis(8-amino-5-iodoquinoline hydroiodide) mercuric iodide.

11. A light-sensitive silver halide emulsion containing a small amount of 4-nitro-dimethylaniline hydroiodide mercuric iodide.

12. A light-sensitive sulfur-sensitized silver halide emulsion containing a small amount of a molecular addition compound of a mercury salt with a nitrogen compound of the class consisting of (1) heterocyclic nitrogen compounds in which at least 3 bonds of the heterocyclic nitrogen atom are attached to carbon, (2) amine-substituted mononuclear aromatic compounds in which 3 bonds of the amino-nitrogen atom are attached to carbon, (3) their halogen acid salts, and (4) the halogen acid salts of aliphatic amines containing at least 3 carbon atoms.

13. The emulsion of claim 12 which is additionally chemically sensitized with gold salts.

14. A light-sensitive sulfur sensitized silver halide emulsion additionally chemically sensitized with gold salts and containing a small amount of a double salt of a pyridine hydrohalide and a mercuric salt.

15. The emulsion of claim 12 which is additionally chemically sensitized with reduction sensitizers.

16. A light-sensitive sulfur sensitized silver halide emulsion additionally chemically sensitized with reduction sensitizers and containing a small amount of a double salt of a pyridine hydrohalide and a mercuric salt.

.17. The emulsion of claim 1 which is chemically sensitized with reduction sensitizers.

18. The emulsion of claim 12 which is additionally chemically sensitized with both gold salts and reduction sensitizers.

19. The method of reducing fog and loss of speed upon storage of a silver halide emulsion, which comprises incorporating in said emulsion at any stage prior to coating a small amount of a molecular addition of a mercury salt with a nitrogen compound of the class consisting of (l) heterocyclic nitrogen compounds in which at least 3 bonds of the heterocyclic nitrogen atom are attached to carbon, (2) amine-substituted mononuclear aromatic compounds in which 3 bonds of the aminonitrogen atom are attached to carbon, (3) their halogen acid salts, and (4) the halogen acid salts of aliphatic amines containing at least 3 carbon atoms.

20. The' method of reducing fog and loss of speed upon storage of a silver halide emulsion, which comprises incorporating in said emulsion at any stage prior to coating, :1 double salt of a 5-iodopyridine hydroiodide and a mercuric halide.

References Cited in the file of this patent UNITED STATES PATENTS 1,738,530 Frankenburger et al. Dec. 10, 1929 2,059,642 Kankelwitz Nov. 3, 1936 2,487,850 Carroll Nov; 15, 1949 2,540,086 Baldsiefen et al. Feb. 6, 1951 FOREIGN PATENTS 633,159 Great Britain Dec. 12, 1949 

1. A LIGHT-SENSITIVE SILVER HALIDE EMULSION CONTAINING A SMALL AMOUNT OF A MOLECULAR ADDITION COMPOUND OF A MERCURY SALT WITH A NITROGEN COMPOUND OF THE CLASS CONSISTING OF (1) HETEROCYCLIC NITROGEN COMPOUNDS IN WHICH AT LEAST 3 BONDS OF THE HETEROCYCLIC NITROGEN ATOM ARE ATTACHED TO CARBON, (2) AMINE-SUBST ITUTED MONONUCLEAR AROMATIC COMPOUNDS IN WHICH 3 BONDS OF THE AMINONITROGEN ATOM ARE ATTACHED TO CARBON, (3) THEIR HALOGEN ACID SALTS, AND (4) THE HALOGEN ACID SALTS OF ALIPHATIC AMINES CONTAINING AT LEAST 3 CARBON ATOMS. 